This invention relates to improvements in methods of casting molten metal and more particularly to such methods concerned with the utilization of a vacuum means for filling the mold in the casting procedures.
One of the important objects of the present invention is to produce billets from selected alloys which may be further efficiently processed in a rolling mill, through an extrusion press, used for electrodes or otherwise that are of uniform density with only a minor variable in the analysis of the cast product and which are completely free of air pockets or air bubbles that can adversely affect final processing. These objectives are difficult to achieve in known and commonly used hand casting methods where analysis of finished pieces from successive castings have shown variations in the metal content of as much as .+-. 3% that is attributable to inevitable slight variations in temperature and timing inherent in hand casting methods.
The use of a vacuum means for filling a mold in the casting of metal is not a new concept as seen in U.S. Pat. No. 914,679 (1909) and further utilized in principle in such patents as U.S. Pat. Nos. 2,970,350 (1961) and 3,774,668 (1973) and I have employed the vacuum concept in further providing improvements that enhance the quality of the finished casting.
Accordingly, it is another important object herein to provide a water cooled mold whereby upon extension of one end thereof into a pot of molten metal and the filling of the mold by extracting the air therein under vacuum, the casting is quickly cooled sufficiently to harden by directing water rapidly under pressure through the water jacket on the mold.
Another object is to provide the cooling water with a velocity sufficient to prevent any flash steaming and thus maintain consistency in the cooling effect throughout the entire length of the casting.
A further object is to provide a water cooled, vacuum associated mold as characterized wherein upon removal of the mold from the pot with the water cooling function in operation, cessation of the water flow permits contained heat in the casting to reheat the mold and expand it sufficiently so that the casting can drop free of the mold upon release of the vacuum.
Still another object is to provide a mold of the above class which includes control means to precisely limit the penetration of the mold into the molten metal according to predetermined calculations and which can be quickly and easily adjusted as required by different levels of the molten metal due to repeated withdrawals thereof by successive castings.
The foregoing objects and such further objects as may appear herein, or be hereinafter pointed out, together with the advantages of this invention will be more fully discussed and developed in the more detailed description of the accompanying drawings.